Media consumptions studies attempt to estimate population behaviors based on observed activities of a population sample. A panel of volunteers (known typically as panelists) agrees to be monitored while engaging in specific activities such as watching television or grocery shopping. A panel operator designs the panel, including the composition of the panelists. The panelists' behaviors are recorded and analyzed, and then extrapolated to the larger population.
Assembling such a panel can be time consuming and expensive. Furthermore, errors in the data collection efforts will adversely affect the validity of any analysis and extrapolation.